This project is to develop a Rolling Joint Prosthetic Foot and Ankle (RJFA) with a newly invented cam rolling ankle joint, which kinematic and dynamic outcome (moment of resistance to deflection in three planes) is closer to the biological prototype. The specific aims of the project, are: (1) optimize the independent prototype parameters, such as geometry of rolling surfaces, rigidity of elastic band, methods of bands's attachment, stiffness of the tibia and foot components,in accordance with a mathematical model developed; (2) manufacture and mechanically test two kind of prototypes at the Ohio Willow Wood Company (OWW), Mt. Sterling, OH; (3) conduct a pilot biomechanical study of walking (4-5 subjects) with the RJFA prototypes to prove a hypothesis that a new mechanism with the proposed outcome improves a BK amputee gait by normalizing of the existing knee performance and increasing stability of stance. Potential commercial application of the proposed research upon completing Phase I and Phase Il is the creation of a new product line at the OWW. Long term objective of this research is development of durable and economical RJFA, which will enhance performance of an amputee by utilizing new mechanical features without increase in the cost. PROPOSED COMMERCIAL APPLICATION: Potential commercial application of the proposed research is the creation of a product line of a new Prosthetic Rolling Joint Foot and Ankle. This new device will enhance performance of an amputee without increase in cost, which will result in a highly competitive product.